In recent years, an online commerce is widely practiced using a content distribution system, in which a content distribution server storing a file related to a content such as a game, music, a movie, a novel, or the like, and a user terminal device of a user who uses the content are connected via a telecommunication circuit such as Internet, and a file related to the content within the content distribution server can be downloaded into the user terminal device.
As such a content distribution system, there is proposed a system disclosed in Japanese Unexamined Patent Application Publication No. 2004-171377, for example, and the content distribution system is configured such that a user terminal device for transmitting an identification code of a content file; an authentication server for receiving the identification code from the user terminal device to authenticate the identification code; and a distribution server, in which a content file is stored, for transmitting the content file to the user terminal device are connected via Internet.
The identification code of the content file is described in a card or the like appropriately sold. A user purchases the card on which the identification code related to a desired content is described so that the identification code is known, inputs the identification code into the user terminal device, and transmits to the authentication server.
The authentication server is provided with a storing section in which the identification code and data indicating whether the identification code is an authenticated code are stored in a manner to be associated with each other, and upon receipt of the identification code transmitted from the user terminal device, refers to the data stored in the storing section to confirm whether the received identification code is the authenticated code. In the case of not the authenticated code, the authentication server transmits the identification code and an address of the user terminal device to the distribution server, and updates the data stored in the storing section to change the identification code to the authenticated code. In the case of the authenticated code, the authentication server sends back an error message to the user terminal device.
When receiving the identification code and the address of the user terminal device which are transmitted from the authentication server, the distribution server transmits a content file corresponding to the received identification code to the user terminal device based on the received address of the user terminal device.
According to the thus-configured content distribution system, whether the identification code is the authenticated code is managed by the authentication server, and the content file is transmitted only once per identification code to the user terminal device from the distribution server, and thus, an unauthorized use of the content by using a used identification code which is wrongly obtained by the user is prevented.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-171377